Electrical contact assembly



^ Jan 10, 1967 R. L. PEEK, JR., ETAL 3,297,850

ELECTRICAL CNTACT ASSEMBLY Filed April 19,V 1965l NVENTORS ROBERT L.PEEK JR. THEODORE S. SIPOS AGEA/Ts ,61490627 Qu/19W Jan. 10, 1967 y R.L. PEEK, JR.. ETAL 3,297,850

ELECTRICAL CONTACT ASSEMBLY vFiled April 19, 1965 2 Sheets-Sheet 2NVENTORS ROBERT l PEEK JR. THEODORE S. SIPOS AGENTS United States PatentO M 3,297,850 ELECTRICAL CONTACT ASSEMBLY Robert L. Peek, Jr.,Smithtown, N.Y., and Theodore S. Sipos, Ottawa, Ontario, Canada,assignors to Northern Electric Company Limited, Montreal, Quebec, CanadaFiled Apr. 19, 1965, Ser. No. 448,984 Claims. (Cl. 2Mb-166) Thisinvention relates to an electrical contact assembly and is particularlyadaptable for use in a sub-assembly of a communications crossbar switch.In the design of present day crossbar switches for communicationsswitching systems, it is important that the switches be as compact andas light as possible. This reduces floor space requirements for mountingthe switches and lessens the floor load per unit area.

However, attempts to make such switches more compact have introducedfurther problems. For example, electrical contacts in the form of thinresilient spring members must be extended to the rear of a crossbarswitch to serve as -terminals for connection of wires. Thesevconnections are conventionally made by soldering techniques. With morecompact switches, the terminals of necessity become more fragile andmore closely spaced making it diiiicult to solder wires to them. Thiscan be a serious problem when it is recognized that the total cost of aswitch is largely dependent on the cost of making the electricalconnections.

This problem has led switch designers to look for alternative ways ofconnecting wires to terminals. One known way that is gaining wideacceptance is the technique of solderless wire wrapping. This isaccomplished by wrapping wire around substantially rigid terminalshaving sharp corners as found in a rectangular cross-sec tion. Thespacing of such terminals can be minimized by making the cross-sectionsubstantially square. Solderless wire wrapping techniques are known tobe less expensive than lsoldering techniques and also to require lessworking space while making the connections. However, previous attemptsto connect rigid terminals to resilient spring members while at the sametime accomplishing the ,desired compactness of a switch have not beenentirely successful.

We have invented an electrical contact assembly that permits theconstruction of compact switch assemblies; that permits use ofsolderless wire wrapping; and that uses a minimum number of parts.

According to our invention, iirst and second elongated electricallyconductive contact support members are arranged to be supported at aregion intermediate their ends. On end of each member is of relativelythin crosssection for resilience and is arranged to carry an electricalcontact. The other end of each member is of relatively thickcross-section for rigiditythe thick cross-section extending from itsother end -into the intermediate regi-on. Means are provided forsupporting an insulator between the two contact support members in theintermediate region whereby the members are insulated and separated fromeach other and whereby the one end of the first member is substantiallycoextensive with the `one end of the second member.

The advantages `of our invention will be more readily apparent byconsidering its application to a crossbar switch. In .a typical 200crosspoint six wire crossbar 4 3,297,850 Patented Jan. 10, 1967 ICCswitch, there are 20 vertical units, each requiring 60 terminals for thecontact carrying resilient spring members. Each of these contactcarrying members is adapted to mate with an associated fixed contactcarrying member. The fixed members are usually multiplied together andbrought out to a common terminal at the back of the switch. It is usualto stack a number of the resilient members and support them in what iscornmonly known as a pile-up. In the past, these members have beenseparated and insulated from each other by metallic spacers and/orinsulators. The sub-assemblies of resilient members were attached to andclamped to the switch frame by insulated screws. Because the contactsupport member according to our invention, is supported at a regionincluding its thick crosssection, this region serves as the separatorand only a thin insulator is required to insulate two members from eachother. The extremity of the end of the member that is of relativelythick cross-section can be made rectangular and preferably square ormaking connections by solderless wire wrapping.

In one embodiment of our invention as applied to a crossbar switch, weemploy a sheet carrying a plurality of fixed contacts, one associatedwith each of the contact support members. This multiple board can beadvantageously made of insulating material to serve both as a pile-upinsulator and as the xed contact support member, thereby contributing tothe compactness `of the final switch assembly and to the reduction ofparts.

It has also been common in the past to support and assemble the fixedcontact support members independently of the resilient movable contactsupport members with the fixed contacts being interspersed between themovable contacts. Presumably, this was done to economize on metallicmaterial .and to reduce weight because the fixed Contact support memberwould otherwise have had to be extended toward the back end of themovable -contact support members to permit a common support. Again, thefixed contacts were supported, separated and insulated from each otherby metallic spacers, insulators and insulated screws. The fixed contactsupport members were supported in the pile-up between adjacent columnsof contact pairs thereby using up space between these columns to locatethe supporting structure. In contrast, our insulated sheet for carryingthe iixed contacts can serve as an insulator between the iixed contactsand the movable contacts, with the complete assembly of fixed andmovable contacts being supported in the thick cross-section region ofeach contact support member. The insulated sheet therefore eliminatesall of the support structure for the iixed contacts. ln addition, withthe assembly being supported in the thick cross-section region of thesupport member, the spacing between adjacent contact support members canbe reduced to permit construction of a more compact switch.

The iixed contact carrying insulated `sheet can be made lighter than thepreviously used metal supports there'by realizing a weight saving forthe switch.

We have succeeded in making a 200 crosspo-int six wire crossbar switchin accordance with our invention that occupies a volume of only 460cubic inches compared with 1925 cubic inches of a typical prior artswitch with similar capacities. The weight of our switch has beenreduced to 15 lbs. compared with 58 lbs. of the typical prior artswitch. The back of our switch contains 1520 terminals suitable for wirewrapping in a space measuring 2l inches X 4.4 inches.

While the advantages of our invention 'have been described in connectionwith a communications crossbar switch, it will be understood by thoseskilled in the art that the invention is applicable to ot-her mechanismsemploying an electrical contact assembly. For example, our invention canbe used in the contact assembly of an elec'- romechanical relay.

Preferred embodiments of our invention will now be described, by way ofexample, with reference to the accompanying drawings in which: v

FIG. 1 is an elevation view of a contact support member representativeof the prior art;

FtIG. 2 is an elevation view of a contact support member according toour invention;

FIG. 3 shows an electrical contact assembly according to our inventionsui-table for use in ya relay;

IFIG. 4 (shown on the sheet of drawings containing FIG. 6) is anembodiment of our invention as applied -to a vertical sub-assembly of Vacrossbar switch;

FIG. (shown on the sheet of drawings containing FIGS. l to 3) is anelectrical contact assembly wherein an insulated sheet is used `tosupport the fixed contacts; and FIG. 6 is an application of the assemblyof FIG. 5 to a vertical sub-assembly of a crossbar switch. FIG. 1 showsa typical contact support member of the prior art. Two elongated,electrically conducting resilient contact support members 11, 111a carryelectrical contacts 12, 12a at one end, and are extended at the otherend to form terminals |13, 13a for connection of wires byl soldering.The support members 11, 11a are supported, spaced and insulated fromeach other by means of a metal spacer 14 a :pair of insulators -15 andinsulated screws |16. .In some cases, `a single thicker insulator couldbe used in lieu of the metal spacer. A pair of xed contacts 17, -17a areheld in mating position with the contacts 12, 12a respectively by meansnot shown. A card .1'8 retains the support members 11, 11a in a positionto keep the contacts =12, 12a and ,17, -17a apart and is adapted to move-to `allow the contacts to mate under the influence of spring tension onthe support members 11, 11a. If the terminals 13, 13a are closelyspaced, soldering becomes difiicult.

FIG. 2 shows the arrangement of FIG. 1 modified according to ourinvention. Elongated, electrically conductive contact support members2-1, 21a have one of their ends 22, 22a made of relatively thincross-section for resilience and are yarranged to carry electricalcontacts 23, 23a. The other ends 24, 24a of the members 21, 21a are ofrelatively thick cross-section for rigidity. The extremity of the ends24, 24a kare of rectangular and preferably of substantially squarecross-section to serve as terminals 25, 25a for connecting wires bysolderless wire wrapping. The support members 21, 21a are arranged to besupported in la region intermediate its ends -in the thick cross-sectionby support means such as insulated screws 2'6. The ythick cross-sectionregion provides rigidity to the assembly and serves to separate thesupport member 21 from support member 21a. These members are ins-ulatedfrom each other by a single thin insulator 27. The ends 24, 24a are ofthicker crosssection where they are supported than at their extremities.The mating of the movable contacts 23, 23a with fixed contacts 28, 28aby means of the card 29 is accomplished in the same manner as in FIG. 1.

The ends 22, 22a can be conveniently formed of pieces of resilientmaterial and the thick cross-section ends 24, 24a can be formed ofpieces of rigid material, the pieces thereafter being joined together inoverlapping relationpreferably by conventional welding techniques. Thesupport members 21, 21a are adapted to be supported in the overlappedregion.

as a make contact assembly for an electro-mechanical relay. Two contactsupport members 31, 31a of the type shown in FIG. 2 are assembled andsupported in their thick cross-section region and insulated by a singleinsulator 32 such that contacts 33, 33a are normally in separa-ted,mutual face-to-face relation. Contact 33a can be moved to mate withcontact 33 by .the action of the card 34 in the well lknown manner. Inthis case, the support member 31 of the lixed contact 33 may lbe rigidrather than resilient, or be supported at its forward end by a iixedcard or -other means not shown.

FIG. 4 shows an embodiment of our invention that is useful in a crossbarswitch vertical sub-assembly. A number of contact support members 41 ofIlhe type shown in FIG. 2 are mounted in a row. A number of rows ofsupport members 41` are clamped in a stack or pile-up between metal bars43 by means of insulated screws 44. Each row of support members 41 isseparated from its yadjacent -row of support members in the stack by'its thick cross-section and an insulator 45. A number of fixed contacts`46 are interposed between the support members 41 and are carried bymetal plates l47 which are supported and assembled by insulated screwsand spacers 48. The support members `41 can be tensioned so that theircontacts 42 will mate with associated fixed contacts V46 upon movementof the cards 49 in the well Iknown manner.

FIG. 5 shows an embodiment of our invention which uses an insulatedsheet or multiple board `51 to carry the fixed contacts 52. A pair ofcontact support members 53 of the type shown in FSIG. y2 are mounted onthe board 51 so lthat their contacts 54 are disposed in spaced, face--to-face relationship with the fixed contacts '52. The extremities ofthe thick cross-section end of the support members 53 extend beyond theedge of the board 51 to serve as tenminals 55 for connecting wires bywire wrapping.

The fixed contacts 52 are multipled together on the board 51 by a thinmetal pattern 56. The pattern 56 is extended toward the edge of theboard 51 and is connected to a terminal 57which extends beyond the edgeof the board for connecting wires by wire wrapping. The support members5'3 'and the terminal 517 are supported and assembled to the board 51 byscrews 58. :Upon movement of the cards 59 the movable contacts 54 willmate with the Ifixed contacts S2 in the well known manner.

It should ibe noted that the support members 53 are separated from thelixed contacts 52 by their thick cross'- section. The board 51 servesnot only as a support member for the fixed contacts 52 but also toinsulate them from the support members 53.

FIG. 6 shows a modification of the vertical subassembly of a crossbarswitch illustrated in FIG. 4 to incorporate the embodiment of FIG. 5.The arrangement is similar to the one shown in FIG. 4 except that thexed contacts are carried by insulated sheet or multiple board 51 of thetype shown in FIG. 5. Now, the pile-up of movable contact supportmembers 41 and the insulated boards 51 can be supported inthe thickcross-section of the members 41. With the elimination of the separatesupport structure for the fixed contacts (see elements 47 and 48 of FIG.4), the adjacent support members 41 can be more closely spaced to permitconstruction of a more compact switch. The boards 51 not only insulatethe iixed contacts 52 from the contact support members 41 but alsoinsulate contact support members 41 from each other in the pile-up.

The sub-assemblies of contact support members as illustrated in FIGS. 4and 6 can be conveniently fabricated by well known techniques. A row ofthe thin, resilient ends of the contact support members can be punchedfrom a single sheet of metal with thin end connections retained so thatthe layer of spring contacts can be handled and assembled as a unit. Therow of rigid, thick crosssection ends can be punched from a single sheetof metal with end connections retained in a similar Way. The row ofresilient and rigid ends can be assembled by welding them together. Theend connections can then be sheared off to separate the assembledmembers electrically and mechanically from each other.

Before shearing off the terminal end members, the spring and terminalsub-assembly can be mounted on the multiple board and secured to it bybonding or other means. After the terminal end connections are shearedoff, the resulting sub-assembly comprises one complete set of fixed andmoving contacts for a vertical unit. For a six-Wire switch, six of thesesub-assemblies are stacked and bolted together to provide the completecontact assembly of a vertical unit.

We have shown that we have invented an electrical contact assembly thatis useful for compact switch assemblies; that permits advantageous useof solderless wire wrapping; and that uses a minimum number of parts.

What is claimed is:

1. An electrical contact assembly comprising:

(a) first and second elongated, electrically conductive contact supportmembers, one end of each said member carrying an electrical contact `andbeing of relatively thin cross-section for resilience, the other end ofeach said member being of relatively thick crosssection for rigidity,the thick cross-section of each said member extending from its other endinto a region intermediate its ends;

(b) and insulator;

(c) and support means supporting the insulator between the two saidmembers in said intermediate region, whereby said members are insulatedand separated from each other, and whereby the one end of said firstmember is substantially coextensive with the one end of said secondmember.

2. An electrical contact assembly as defined in claim 1 wherein theextremity of the other end of each said member is of substantiallysquare cross section, and the other end of each said member is ofgreater cross section in said intermediate region than at its extremity.

3. An electrical contact assembly as defined in claim 2 wherein the oneend of each said member is formed of a piece of resilient material andthe other end of each said member is formed of a piece of rigidmaterial, the two pieces of each said member joined in overlappingrelationship, and wherein the support means is applied across theoverlap of the two pieces of each said member, and wherein the insulatoris disposed between the piece of resilient material of said first memberand the piece of rigid material of said second member.

4. An electrical contact assembly comprising:

(a) a plurality of elongated, electrically conductive contact supportmembers, one end of each said member carrying an electrical contact andbeing of relatively thin cross-section for resilience, the other end ofeach said member being of relatively thick crosssection for rigidity,the thick cross-section of each said member extending from its other endinto a region intermediate its ends;

(b) a plurality of insulators;

(c) support means supporting all said members in said intermediateregion of each said member into a stack with an insulator interposedbetween each adjacent said member, whereby said members are insulatedand separated from each other, and whereby the one end of all saidmembers are substantially coextensive, with all contacts facing in thesame direction;

(d) and a plurality of electrically conductive fixedcontact carryingmembers one associated with each said support member, said fixed memberssupported independently of said support members `and disposed in a stackwhereby their individual contacts are each in a separated, face-to-facerelationship with an individual contact of an associated said supportmember.

5. An electrical contact assembly as defined in claim 4 wherein theextremity of the other end of each said support member is ofsubstantially square cross section, and the other end of each saidsupport member is of greater cross section in said intermediate regionthan at its extremity.

6. An electrical contact assembly as defined in claim 5 wherein the oneend of each said support member is formed of a piece of resilientmaterial and the other end of each said support member is formed of apiece of rigid material, the two pieces of each member joined inoverlapping relation, wherein the support means is applied across theoverlap of the two pieces of each member and wherein each insulator isdisposed between the piece of resilient material of one said supportmember and the piece of rigid material of an adjacent said supportmember.

7. An electrical contact assembly comprising:

(a) a plurality of electrical contact assemblies as defined in claim 6;

(b) and support means supporting said assemblies in a spaced-apart rowwhereby the individual said support members at each level of theirstacks are disposed in the same plane with their one ends beingsubstantially coextensive, and whereby the individual said fixed membersat each level of their stacks are disposed in the same plane.

8. An electrical contact assembly as defined in claim 7 wherein saidassembly is part of the vertical assembly of a crossbar switch.

9. An electrical contact assembly comprising:

(a) a plurality of elongated, electrically conductive contact supportmembers, one end of each said member carrying an electrical contact andbeing of relatively thin cross-section for resilience, the other end ofeach said member being of relatively thick crosssection for rigidity,the thick cross-section of each said member extending from its other endinto a region intermediate its ends;

(b) a sheet carrying a row of electrical contacts on one side thereof,one contact associated with each said member;

(c) and support means supporting each said member in said intermediateregion against the sheet whereby each contact of the sheet is insulatedfrom said members and is disposed in face-to-face relationship with thecontact of its associated said member.

10. An electrical contact `assembly as defined in claim 9 wherein thesheet is an insulated sheet and serves to insulate each contact of thesheet from said members.

11. An electrical contact assembly as defined in claim 10 including athin metal pattern attached to the sheet, the row of electrical contactscarried by said pattern.

12. An electrical contact rassembly as detined in claim 11 wherein theextremity of the other end of each said member is of substantiallysquare cross-section, and the other end of each said member is ofgreater cross-section in said intermediate region than at its extremity.

13. An electrical contact assembly as defined in claim 12 wherein oneend of each said member is formed of a piece of resilient material `andthe other end of each said member is formed of a piece of rigidmaterial, the two pieces of each said member joined in overlappingrelation, and wherein the support means is applied across the overlap ofthe two pieces of each said member.

14. An electrical contact assembly comprising:

(a) a plurality of electrical contact assemblies as defined in claim 13;

(b) and support means supporting said assemblies in said intermediateregion of each said member into a stack of assemblies with the otherside of the sheet of one said assembly mounted against the individualsaid members of an adjacent said assembly, whereby said members on-theone said assembly are insulated and separated from said members on theadjacent said assembly. v 15. An electrical contact assembly as dened inclaim 14 wherein said assembly is part of the vertical assembly of across'bar switch, and each of the contacts carried by the pattern aremultiplied together and connected to 10 a terminal.

- References Cited by the Examiner UNITED STATES PATENTS Mason 339-267 XBuhrendorf 174-94 Ayer 174-88 Derkas 174-94 X Ruckriegel et al. 200-166X

1. AN ELECTRICAL CONTACT ASSEMBLY COMPRISING: (A) FIRST AND SECONDELONGATED, ELECTRICALLY CONDUCTIVE CONTACT SUPPORT MEMBERS, ONE END OFEACH SAID MEMBER CARRYING AN ELECTRICAL CONTACT AND BEING OF RELATIVELYTHIN CROSS-SECTION FOR RESILIENCE, THE OTHER END OF EACH SAID MEMBERBEING OF RELATIVELY THICK CROSSSECTION FOR RIGIDITY, THE THICKCROSS-SECTION OF EACH SAID MEMBER EXTENDING FROM ITS OTHER END INTO AREGION INTERMEDIATE ITS ENDS; (B) AND INSULATOR; (C) AND SUPPORT MEANSSUPPORTING THE INSULATOR BETWEEN THE TWO SAID MEMBERS IN SAIDINTERMEDIATE REGION, WHEREBY SAID MEMBERS ARE INSULATED AND SEPARATEDFROM EACH OTHER, AND WHEREBY THE ONE END OF SAID FIRST MEMBER ISSUBSTANTIALLY COEXTENSIVE WITH THE ONE END OF SAID SECOND MEMBER.